Structure for microelectromechanical systems (MEMS) devices to control pressure at high temperature

ABSTRACT

Various embodiments of the present disclosure are directed towards an integrated chip including a capping structure over a device substrate. The device substrate includes a first microelectromechanical systems (MEMS) device and a second MEMS device laterally offset from the first MEMS device. The capping structure includes a first cavity overlying the first MEMS device and a second cavity overlying the second MEMS device. The first cavity has a first gas pressure and the second cavity has a second gas pressure different from the first cavity. An outgas layer abutting the first cavity. The outgas layer includes an outgas material having an outgas species. The outgas material is amorphous.

BACKGROUND

Microelectromechanical systems (MEMS) is a technology that integratesminiaturized mechanical and electro-mechanical elements on an integratedchip. MEMS devices are often made using micro-fabrication techniques. Inrecent years, MEMS devices have found a wide range of applications. Forexample, MEMS devices are found in cell phones (e.g., accelerometers,gyroscopes, digital compasses), pressure sensors, micro-fluidic elements(e.g., valves, pumps), optical switches (e.g., mirrors), etc. For manyapplications, MEMS devices are electrically connected toapplication-specific integrated circuits (ASICs), and to externalcircuitry, to form complete MEMS systems. Commonly, the connections areformed by wire bonding, but other approaches are also possible.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of some embodiments of anintegrated chip having an outgas layer and a firstmicroelectromechanical systems (MEMS) device disposed within a firstcavity, and a getter layer and a second MEMS device disposed within asecond cavity.

FIGS. 2-4 illustrate cross-sectional views of integrated chips accordingto some alternative embodiments of the integrated chip of FIG. 1.

FIGS. 5A-B illustrate some embodiments of a MEMS accelerometer.

FIGS. 6A-B illustrate some embodiments of a MEMS gyroscope.

FIGS. 7-22 illustrate cross-sectional views of some embodiments of amethod of forming an integrated chip having an outgas layer and a firstMEMS device disposed within a first cavity, and a getter layer and asecond MEMS device disposed within a second cavity.

FIG. 23 illustrates a methodology of some embodiments of forming anintegrated chip having an outgas layer and a first MEMS device disposedwithin a first cavity, and a getter layer and a second MEMS devicedisposed within a second cavity.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

MEMS devices may be used in a wide range of applications, for example,motion sensors are used for motion-activated user interfaces in consumerelectronics such as smartphones, tablets, gaming consoles, smart-TVs,and in automotive crash detection systems. To capture a complete rangeof movements within a three-dimensional space, multiple MEMS devices maybe integrated onto a single integrated chip. For example, motion sensorsoften utilize an accelerometer and a gyroscope in combination. Theaccelerometer detects linear movement. The gyroscope detects angularmovement. To meet consumer demand for low cost, high quality, and smalldevice footprint, the accelerometer and the gyroscope can be formed frommicroelectromechanical systems (MEMS) devices, which are integratedtogether on a same substrate. Although they share the same substrate,and hence a same manufacturing process, the accelerometer and thegyroscope utilize different operating conditions. For example, thegyroscope is often packaged in a vacuum for optimal performance. Incontrast, the accelerometer is often packaged at a predeterminedpressure (e.g., 1 atmosphere) to produce a smooth frequency response.

Thus, the present disclosure is directed towards an integrated circuithaving two or more MEMS devices integrated together on a singlesubstrate. According to some processes for forming the integratedcircuit, an interconnect structure is formed over a semiconductorsubstrate. An outgas layer comprising an outgas species is formed in afirst region of the interconnect structure and a getter layer is formedin a second region of the interconnect structure laterally offset fromthe first region. A MEMS substrate comprising one or more moveableelements for a first MEMS device and one or more moveable elements for asecond MEMS device is bonded to the interconnect structure. A cappingstructure comprising a first cavity and a second cavity is bonded to theMEMS substrate, such that the first cavity overlies the first MEMSdevice and the second cavity overlies the second MEMS device. Bondingthe capping structure to the MEMS substrate seals the first and secondcavities. The outgas layer abuts the first cavity and the getter layerabuts the second cavity, in which the first cavity has a first gaspressure and the second cavity has a second gas pressure. The outgaslayer is configured to maintain or sustain the first gas pressure andthe getter layer is configured to maintain or sustain a vacuum in thesecond cavity, such that the first gas pressure is greater than thesecond gas pressure.

A challenge with the above process is related to an ability of theoutgas layer to outgas the outgas species at high temperatures (e.g.,above 400 degrees Celsius). For example, the outgas layer may comprisean outgas material (e.g., silicon oxide deposited by a high densityplasma (HDP) chemical vapor deposition (CVD) process) configured tofacilitate outgassing and maintain or sustain the first gas pressure inthe first cavity during operation of the first MEMS device. The outgasmaterial may have a low outgas activation temperature (e.g., less than150 degrees Celsius) and may outgas a majority of the outgas speciesbefore reaching an outgas depletion temperature (e.g., approximately 400degrees Celsius). However, bonding the MEMS substrate to theinterconnect structure may comprise reaching a maximum bondingtemperature (e.g., about 420 degrees Celsius) greater than or equal tothe outgas depletion temperature. Thus, while bonding the MEMS substrateto the interconnect structure, a majority of the outgas species may beoutgassed from the outgas layer into the fabrication chamber. Therefore,the outgas layer may be depleted of the outgas species before sealingthe first cavity. This mitigates an ability of the outgas layer tomaintain, sustain, and/or achieve a predetermined pressure (e.g., 1atmosphere) in the first cavity after fabrication of the first MEMSdevice, thereby decreasing a quality factor, a stability, and/or anendurance of the first MEMS device.

Various embodiments of the present application are directed towards animproved outgas layer configured to continue outgassing the outgasspecies after fabrication of the integrated chip. The integrated chipincludes an interconnect structure overlying a semiconductor substrate.A MEMS substrate comprising one or more moveable elements for a firstMEMS device and one or more moveable elements for a second MEMS deviceoverlies the interconnect structure. A capping structure comprising afirst cavity and a second cavity overlies the MEMS substrate, such thatthe first cavity overlies the first MEMS device and the second cavityoverlies the second MEMS device. An outgas layer comprising an outgasmaterial, such as hydrogenated amorphous silicon (e.g., a-Si:H) with ahigh composition of an outgas species (e.g., hydrogen (H)), abuts thefirst cavity and a getter layer abuts the second cavity. Thus, the firstcavity has a first gas pressure and the second cavity has a second gaspressure less than the first gas pressure. The outgas material has a lowoutgas activation temperature (e.g., about 100 degrees Celsius) andcontinuously outgasses the outgas species at high temperatures (e.g.,greater than 570 degrees Celsius). This is because the outgas materialhas a high composition of the outgas species and/or the outgas materialis amorphous. The random structure of the amorphous outgas materialallows for continued release of the outgas species at high temperatures(e.g., greater than 420 degrees Celsius). Therefore, the outgas layerwill continue outgassing the outgas species after bonding the MEMSsubstrate to the interconnect structure and after sealing the firstcavity, such that the outgas layer may assist achieving, maintaining,and/or sustaining the first gas pressure of the first cavity duringoperation of the first MEMS device. This increases the quality factor,the stability, and/or the endurance of the integrated circuit.

FIG. 1 illustrates a cross-sectional view of some embodiments of anintegrated chip 100 with multiple microelectromechanical systems (MEMS)devices 135, 137 disposed within cavities 136, 140, respectively.

The integrated chip 100 includes a device substrate 101 and a cappingstructure 125, where the device substrate 101 underlies the cappingstructure 125. The device substrate 101 includes a semiconductorsubstrate 102, an interconnect structure 104, and a MEMS substrate 124.In some embodiments, one or more active elements 106 (e.g., transistors)are disposed over and/or within the semiconductor substrate 102. Infurther embodiments, the one or more active elements 106 may includesource/drain regions 108 disposed within the semiconductor substrate 102and arranged below a gate 110. The interconnect structure 104 includesan interconnect dielectric structure 115, a plurality of conductive vias112, and a plurality of conductive wires 114. The conductive vias 112and the conductive wires 114 are disposed within the interconnectdielectric structure 115 and may be electrically coupled to the one ormore active elements 106. The conductive wires 114 may include an upperconductive wire layer 114 a overlying an upper surface of theinterconnect dielectric structure 115 and disposed within a passivationstructure 118.

The passivation structure 118 extends along the upper surface of theinterconnect dielectric structure 115. An upper conductive layer 116overlies the upper conductive wire layer 114 a. A polysilicon layer 122is disposed along a lower surface of the MEMS substrate 124. Conductivebond structures 120 are disposed along protrusions of the MEMS substrate124 that extend through the passivation structure 118. The conductivebond structures 120 may be separated from the MEMS substrate 124 by thepolysilicon layer 122. The conductive bond structures 120 may eachdirectly contact the upper conductive wire layer 114 a. The cappingstructure 125 overlies the MEMS substrate 124, where a first cavity 136and a second cavity 140 are each defined between the capping structure125 and the device substrate 101. The capping structure 125 includes acapping substrate 128 and a capping dielectric layer 126, where thecapping dielectric layer 126 continuously extends along a lower surfaceof the capping substrate 128.

The MEMS substrate 124 includes a first MEMS device 135 and a secondMEMS device 137, which are arranged in the first cavity 136 and thesecond cavity 140, respectively. In some embodiments, the first MEMSdevice 135 includes one or more first moveable elements 134 abutting thefirst cavity 136 and the second MEMS device 137 includes one or moresecond moveable elements 138 abutting the second cavity 140. The one ormore first and/or second moveable elements 134, 138 may each be a partof the MEMS substrate 124. In some embodiments, the first and secondcavities 136, 140 extend into the device substrate 101 and/or thecapping structure 125. For instance, as shown in FIG. 1, the first andsecond cavities 136, 140 each extend into the passivation structure 118to provide clearance for the one or more first and/or second moveableelements 134, 138. In other embodiments, the first and second cavities136, 140 extend into the interconnect structure 104 and/or thesemiconductor substrate 102. In some embodiments, stopper structures 132are disposed within the first and second cavities 136, 140, where thestopper structures 132 are configured to prevent the one or more firstand/or second moveable elements 134, 138 from becoming stuck to thepassivation structure 118. The stopper structures 132 are disposedwithin the passivation structure 118 and each include a first stopperlayer 132 a and a second stopper layer 132 b overlying the first stopperlayer 132 a. In some embodiments, the first stopper layer 132 a isconfigured as an adhesion layer.

A first plurality of hermetic seal boundaries are disposed between theconductive bond structures 120 and the upper conductive wire layer 114a, and a second plurality of hermetic seal boundaries are disposedbetween the capping structure 125 and the MEMS substrate 124. Thus, thefirst cavity 136 has a first gas pressure and the second cavity 140 hasa second gas pressure different than the first gas pressure. In someembodiments, the first and second plurality of hermetic seal boundariesfacilitate the first and second cavities 136, 140 having the differentgas pressures while being disposed laterally adjacent to one another inthe device substrate 101. In some embodiments, the first gas pressure isgreater than the second gas pressure.

An outgas layer 130 is disposed within the passivation structure 118 andabuts the first cavity 136, where the outgas layer 130 is configured tofacilitate and/or assist the first cavity 136 having, maintaining,and/or sustaining the first gas pressure. Further, the upper conductivelayer 116 includes a getter layer 116 a abutting the second cavity 140,where the getter layer 116 a is configured to facilitate and/or assistthe second cavity 140 having, maintaining, and/or sustaining the secondgas pressure. In some embodiments, the getter layer 116 a may be orcomprise a reactive material (e.g., titanium) configured to getter anoutgas species within the second cavity 140. In some embodiments, theoutgas species may, for example, be or comprise oxygen (O₂), argon (Ar),hydrogen (H₂), and/or water (H₂O), or the like. Thus, the getter layer116 a is configured to maintain a vacuum seal of the second cavity 140during operation and/or formation of the integrated chip 100. In someembodiments, the outgas layer 130 comprises an outgas material (e.g.,amorphous silicon (a-Si)) configured to outgas the outgas species intothe first cavity 136, thereby facilitating the first cavity 136 having,maintaining, and/or sustaining the first gas pressure. Thus, the firstgas pressure is greater than the second gas pressure.

In some embodiments, the outgas material may comprise a highconcentration of the outgas species. For example, the outgas materialmay be or comprise hydrogenated amorphous silicon (e.g., a-Si:H) with ahigh composition of the outgas species (e.g., hydrogen (H)). In someembodiments, the outgas material may have an amorphous structure with acontinuous random crystal lattice structure comprising one or moredefects including, for example, dangling bonds. In such embodiments,during fabrication of the outgas layer 130, the outgas material may beformed with a reacting gas (such as SiH₄) comprising the outgas species,such that the outgas species may fill the defects and may, for example,bond the dangling bonds and/or reduce the dangling bond density in theoutgas material. Thus, the outgas layer 130 comprises a high compositionof the outgas species. Because the outgas species may bond the danglingbonds and/or reduce the dangling bond density in the outgas material, itmay require high temperatures to outgas a majority of the outgas speciesfrom the outgas material. This in turn facilitates the outgas layer 130continuously outgassing the outgas species through high temperatures(e.g., temperatures greater than 570 degrees Celsius). Thus, in someembodiments, the outgas layer 130 may facilitate the first gas pressureof the first cavity 136 being greater than the second gas pressure ofthe second cavity 140 during fabrication and/or operation of theintegrated chip 100. In further embodiments, the first MEMS device 135may be configured as an accelerometer and the first gas pressure may,for example, be about 1 atmosphere to produce a smooth frequencyresponse. In such embodiments, the second MEMS device 137 may beconfigured as a gyroscope and the second gas pressure may, for example,be about 0 atmosphere (e.g., a vacuum) to produce smooth angularacceleration.

In some embodiments, during fabrication of the integrated chip 100, theconductive bond structures 120 are bonded to the upper conductive wirelayer 114 a by, for example, a eutectic bond. The eutectic bond isconfigured to form the first plurality of hermetic seal boundaries andmay reach a maximum bonding temperature (e.g., about 435 degreesCelsius). In further embodiments, if the outgas layer 130 comprisesanother outgas material (e.g., silicon dioxide deposited by ahigh-density plasma chemical vapor deposition process) with a low outgasactivation temperature (e.g., less than 150 degrees Celsius) and a lowoutgas depletion temperature (e.g., about 400 degrees Celsius), amajority of the outgas species may be outgassed from the another outgasmaterial after performing the eutectic bond. In such embodiments, amajority and/or all of the outgas species is outgassed before sealingthe first and/or second cavities 136, 140 such that the first cavity 136may not achieve, sustain, and/or maintain the first gas pressure,thereby mitigating performance of the first MEMS device 135. Inembodiments according to the present disclosure, the outgas layer 130comprising the outgas material (e.g., a-Si) ensures a majority of theoutgas species is not outgassed from the outgas material before sealingthe first cavity 136. This, in part, is because the outgas material hasa high outgas depletion temperature (e.g., greater than 570 degreesCelsius). Thus, the outgas layer 130 may continue outgassing the outgasspecies after performing the eutectic bond, after sealing the firstcavity 136, and/or after fabricating the integrated chip 100. This inturn facilities the outgas layer 130 maintaining, achieving, and/orsustaining the first gas pressure in the first cavity 136, therebyincreasing a reliability, endurance, and performance of the integratedchip 100. In some embodiments, when the first MEMS device 135 isconfigured as an accelerometer, by ensuring the first gas pressure isset to a predefined pressure (based on the accelerometer application)the quality factor of the first MEMS device 135 is increased.

FIG. 2 illustrates a cross-sectional view of an integrated chip 200according to some alternative embodiments of the integrated chip 100 ofFIG. 1.

The integrated chip 200 includes a capping structure 125 overlying adevice substrate 101. The device substrate 101 includes a semiconductorsubstrate 102, an interconnect structure 104, a passivation structure118, and a MEMS substrate 124. The semiconductor substrate 102 may, forexample, be or comprise a bulk substrate (e.g., a bulk siliconsubstrate), crystalline silicon (c-Si), such as multi-crystallinesilicon (multi-Si), or monocrystalline silicon (mono-Si), asilicon-on-insulator (SOI) substrate, or another suitable substratematerial. One or more active elements 106 may be disposed on and/orwithin the semiconductor substrate 102. The interconnect structure 104overlies a front-side surface of the semiconductor substrate 102 and isconfigured to provide electrical coupling to the one or more activeelements 106 and/or doped regions within the semiconductor substrate102.

The interconnect structure 104 includes an interconnect dielectricstructure 115, a plurality of conductive wires 114, and a plurality ofconductive vias 112. In some embodiments, the interconnect dielectricstructure 115 may comprise one or more inter-level dielectric (ILD)layers. In further embodiments, the one or more ILD layers may, forexample, be or comprise an oxide, such as silicon dioxide, a low-kdielectric material, another suitable dielectric material, or the like.The plurality of conductive vias and/or wires 112, 114 may, for example,each be or comprise aluminum, copper, aluminum copper, tungsten,titanium, a combination of the foregoing, or the like. The conductivewires 114 may include an upper conductive wire layer 114 a disposedalong an upper surface of the interconnect dielectric structure 115. Insome embodiments, the upper conductive wire layer 114 a may, forexample, be or comprise aluminum, copper, a combination of the foregoingor the like and/or may have a thickness of about 8,000 Angstroms, orwithin a range of about 7,500 to 8,500 Angstroms. In some embodiments, asubstrate pickup region 212 is disposed within the semiconductorsubstrate 102 and may be electrically coupled to ground by way of theinterconnect structure 104.

The passivation structure 118 extends along the upper surface of theinterconnect dielectric structure 115. The passivation structure 118includes one or more passivation layers and/or structures. In someembodiments, the passivation structure 118 includes a first passivationlayer 204 extending across the upper surface of the interconnectdielectric structure 115, a second passivation layer 206 overlying thefirst passivation layer 204, and a third passivation layer 208 overlyingthe second passivation layer 206. In some embodiments, the firstpassivation layer 204 may, for example, be or comprise an oxide, such assilicon dioxide, another suitable oxide, or the like and/or may have athickness of about 4,000 Angstroms, 12,000 Angstroms, or within a rangeof about 11,500 to 12,500 Angstroms. In some embodiments, the secondpassivation layer may, for example, be or comprise silicon rich oxide,silicon dioxide, or another suitable dielectric material and/or may havea thickness of about 1,500 Angstroms or within a range of about 1,250 to1,750 Angstroms. In further embodiments, the third passivation layer 208may, for example, silicon nitride, silicon carbide, or the like and/ormay have a thickness of about 4,000 Angstroms or within a range of about3,500 to 4,500 Angstroms.

An upper conductive layer 116 may overlie the upper conductive wirelayer 114 a. In some embodiments, the upper conductive layer 116 may,for example, be or comprise titanium, tantalum, or the like and/or mayhave a thickness of about 1,800 Angstroms or within a range of about1,600 to 2,000 Angstroms. A dielectric protection layer 202 may overliethe upper conductive layer 116. In some embodiments, the dielectricprotection layer 202 may, for example, be or comprise siliconoxy-nitride, silicon nitride, or the like and/or may have a thickness ofabout 320 Angstroms, or within a range of about 270 to 370 Angstroms.Further, the upper conductive layer 116 may include a getter layer 116 aabutting a second cavity 140, where an upper surface and sidewalls ofthe getter layer 116 a are exposed to the second cavity 140.

A MEMS substrate 124 overlies the interconnect structure 104. Apolysilicon layer 122 extends along a lower surface of the MEMSsubstrate 124. Conductive bond structures 120 are disposed alongprotrusions of the MEMS substrate 124 that extend through thepassivation structure 118. In some embodiments, the MEMS substrate 124may be or comprise a same material as the semiconductor substrate 102.For example, in some embodiments, the MEMS substrate 124 may be orcomprise a bulk substrate (e.g., a bulk silicon substrate), crystallinesilicon (c-Si), such as multi-crystalline silicon (multi-Si), ormonocrystalline silicon (mono-Si), a silicon-on-insulator (SOI)substrate, or another suitable substrate material. The capping structure125 overlies the MEMS substrate 124, where a first cavity 136 and thesecond cavity 140 are each defined between the capping structure 125 andthe device substrate 101. The capping structure 125 includes a cappingsubstrate 128 and a capping dielectric layer 126. In some embodiments,the capping substrate 128 may be or comprise the same material as thesemiconductor substrate 102 and/or the MEMS substrate 124. For example,in some embodiments, the capping substrate 128 may be or comprise a bulksubstrate (e.g., a bulk silicon substrate), crystalline silicon (c-Si),such as multi-crystalline silicon (multi-Si), or monocrystalline silicon(mono-Si), a silicon-on-insulator (SOI) substrate, or another suitablesubstrate material.

In some embodiments, the polysilicon layer 122 may, for example, be orcomprise intrinsic polysilicon, doped polysilicon, or the like. Further,a lower surface and/or sidewalls of the polysilicon layer 122 abuttingthe first and/or second cavities 136, 140 may be rough and/or comprise aplurality of protrusions. In such embodiments, the polysilicon layer 122is configured to prevent stiction with other structures and/or layersdisposed within the first and/or second cavities 136, 140. In someembodiments, the conductive bond structures 120 may, for example, be orcomprise nickel, gold, germanium, aluminum, copper, a combination of theforegoing, or the like. In further embodiments, the capping dielectriclayer 126 may, for example, be or comprise an oxide, such as silicondioxide, another suitable dielectric material, or the like.

Further, the MEMS substrate 124 includes a first MEMS device 135 and asecond MEMS device 137, which are arranged in the first cavity 136 andthe second cavity 140, respectively. In some embodiments, the first MEMSdevice 135 includes one or more first moveable elements 134 abutting thefirst cavity 136 and the second MEMS device 137 includes one or moresecond moveable elements 138 abutting the second cavity 140. The one ormore first and/or second moveable elements 134, 138 may each be a partof the MEMS substrate 124. In further embodiments, stopper structures132 are disposed within the first and second cavities 136, 140, wherethe stopper structures 132 are configured to prevent the one or morefirst and/or second moveable elements 134, 138 from becoming stuck tothe passivation structure 118. The stopper structures 132 are disposedwithin the passivation structure 118 and each include a first stopperlayer 132 a and a second stopper layer 132 b overlying the first stopperlayer 132 a. In some embodiments, the first stopper layer 132 a may, forexample, be or comprise titanium, a titanium rich layer, tantalum, orthe like and/or may have a thickness of about 130 Angstroms or within arange of about 100 to 160 Angstroms. In further embodiments, the secondstopper layer 132 b may, for example, be or comprise silicon nitride,silicon carbide, or the like and/or may have a thickness of about 500Angstroms or within a range of about 450 to 550 Angstroms. Further adielectric capping layer 210 may be disposed between a lateral segmentof the stopper structure 132 and the passivation structure 118. In someembodiments, the dielectric capping layer 210 may, for example, be orcomprise silicon nitride, silicon carbide, or the like, and/or may havea thickness of about 3,500 Angstroms, or within a range of about 3,000to 4,000 Angstroms.

An outgas layer 130 is disposed within the passivation structure 118.The outgas layer 130 has a curved, rounded, and/or concave upper surface130 us abutting the first cavity 136. Further, a lower surface of theoutgas layer 130 is separated from an upper surface of an underlyingdielectric protection layer 202 by a distance ds. In some embodiments,the distance ds is about 3,400 Angstroms or within a range of about3,000 to 3,800 Angstroms. The outgas layer 130 is configured tofacilitate achieving, maintaining, and/or sustaining a first gaspressure of the first cavity 136. The outgas layer 130 comprises anoutgas material. In some embodiments, the outgas material may, forexample, be or comprise hydrogenated amorphous silicon (e.g., a-Si:H)with a high composition of the outgas species (e.g., hydrogen (H)). Inyet further embodiments, the outgas material may, for example, be orcomprise amorphous silicon (e.g., a-Si). In some embodiments, thesemiconductor substrate 102, the MEMS substrate 124, and/or the cappingsubstrate 128 may be or comprise a crystalline form of the outgasmaterial. In further embodiments, the semiconductor substrate 102, theMEMS substrate 124, and/or the capping substrate 128 may each be orcomprise crystalline silicon (e.g., multi-Si or mono-Si) while theoutgas layer 130 may be or comprise amorphous silicon (a-Si). Thus, theoutgas layer 130 may outgas the outgas species at high temperatures(e.g., temperatures greater than 570 degrees Celsius); therebyincreasing a quality factor, a performance, and/or an endurance of theintegrated chip 200.

FIG. 3 illustrates a cross-sectional view of an integrated chip 300according to some alternative embodiments of the integrated chip 200 ofFIG. 2.

As illustrated in FIG. 3, the conductive bond structures 120 may eachcomprise slanted sidewalls extending into the passivation structure 118.Further, the one or more first moveable elements 134 may include a firstgroup of moveable elements 302 and a second group of moveable elements304 laterally adjacent to one another. In some embodiments, the firstgroup of moveable elements 302 are laterally separated from the secondgroup of moveable elements 304 by a segment 124 s of the MEMS substrate124. The first and second group of moveable elements 302, 304 are bothdisposed within and abut the first cavity 136. In further embodiments,the first cavity 136 continuously extends from the first group ofmoveable elements 302 laterally around one or more sides of the segment124 s of the MEMS substrate 124 to the second group of moveable elements304.

FIG. 4 illustrates a cross-sectional view of an integrated chip 400according to some alternative embodiments of the integrated chip 200 ofFIG. 2.

As illustrated in FIG. 4, the one or more first moveable elements 134directly overlie a cavity electrode 114 e disposed within the firstcavity 136. In some embodiments, the cavity electrode 114 e is a part ofthe upper conductive wire layer 114 a. In some embodiments, duringoperation of the integrated chip 400, a change in capacitance betweenthe cavity electrode 114 e and the one or more first moveable elements134 may be detected and converted to an electrical signal. Theelectrical signal may be carried to the one or more active elements 106by way of the interconnect structure 104.

FIGS. 5A-B illustrate various views of some embodiments of a capacitiveMEMS accelerometer 500. It is appreciated that the capacitive MEMSaccelerometer 500 is one possible type of MEMS accelerometer that isincluded for illustration purposes, and does not impose any limitationon the type of MEMS accelerometer utilized in conjunction with theembodiments of the present disclosure.

The capacitive MEMS accelerometer 500 includes first and secondconductive plates 502A, 502 b which are oriented parallel to oneanother. A capacitance of the capacitive MEMS accelerometer 500 isproportional to an area (A) of the first and second conductive plates502A, 502B, as well as a distance (d) between them. Therefore, thecapacitance changes if the distance (d) between the first and secondconductive plates 502A, 502B changes. The second conductive plate 502Bis rigidly attached to an assembly 504. The first conductive plate 502Ais elastically attached to the assembly 504 by springs 506.

When the capacitive MEMS accelerometer 500 undergoes a linearacceleration event along a direction parallel to d, the secondconductive plate 502B moves with the assembly 504, while the firstconductive plate 502A initially does not. Instead, the springs 506expand, allowing the first conductive plate 502A to initially remainstationary. The resulting change in capacitance caused by the movementof the first conductive plate 502A relative to the second conductiveplate 502B can be used to determine a magnitude and/or a direction ofthe acceleration.

Upon completion of the linear acceleration event, the first conductiveplate 502A will oscillate about an equilibrium position until a dampingeffect of air friction slows and eventually stops it. It is thereforedesirable in some embodiments to tune the damping effects of the airfriction to efficiently detect a first linear acceleration event, whiledamping oscillation from the first linear acceleration event in enoughtime to detect a subsequent linear acceleration event. The dampingeffects of the air friction can be tuned by a gas pressure of a gassurrounding the capacitive MEMS accelerometer 500. In some embodiments,a gas pressure on an order of about 1 atmosphere can achieve effectivedamping. It is further appreciated that the exemplary capacitive MEMSaccelerometer 500 of FIGS. 5A-B is a “1-axis” accelerometer. In order todetect a complete range of linear accelerations in a three-dimensional(3D) space, three or more orthogonally oriented capacitive MEMSaccelerometers 500 can be utilized together to form a “3-axis”accelerometer.

FIGS. 6A-B illustrate various views of some embodiments of a ring MEMSgyroscope 600. FIG. 6A illustrates a top view of the ring MEMS gyroscope600. FIG. 6B illustrates a cross-sectional view of the ring MEMSgyroscope 600. It is appreciated that the ring MEMS gyroscope 600 is onepossible type of MEMS gyroscope that is included for illustrationpurposes, and does not impose any limitation on the type of MEMSgyroscope utilized in conjunction with the embodiments of the presentdisclosure. The ring MEMS gyroscope 600 includes an annular ring 602.The annular ring 602 is supported in free-space by spokes 604, which areattached at first and second nodes 606A, 606B.

During operation of the ring MEMS gyroscope 600, the annular ring 602vibrates at a resonant frequency. Actuators or transduces (not shown)are attached to the upper surface of the annular ring 602 at the firstand second nodes 606A, 606B, and are electrically connected to bond padson the spokes 604. The actuators or transducers drive the annular ring602 into a mode of vibration at resonance. When the ring MEMS gyroscope600 is in a resonant state, and not subjected to any angularacceleration, first nodes 606A move radially, while the second nodes606B remain stationary. However, when the ring MEMS gyroscope 600 issubjected to an angular acceleration event (e.g., rotation 608), theCoriolis force changes the resonate state of the annular ring 602, whichcauses the second nodes 606B to move. By detecting the relative movementof the first and second nodes 606A, 606B, the angular acceleration ofthe ring MEMS gyroscope 600 can be measured.

Unlike the capacitive MEMS accelerometer 500, which oscillates during alinear acceleration event, the annular ring 602 of the ring MEMSgyroscope 600 is maintained in a resonant state while in operation. Assuch, the damping effects of air friction are not desired, as theyrequire additional power from the actuators or transducers to drive theannular ring 602 into the resonant state. It is therefore desirable, insome embodiments, to negate the damping effects of the air frication toefficiently detect an angular acceleration event by sealing the ringMEMS gyroscope 600 in a vacuum. The vacuum my increase a performance ofthe ring MEMS gyroscope 600 by suppressing energy dissipation due to airfriction.

FIGS. 7-22 illustrate cross-sectional views 700-2200 of some embodimentsof a method of forming an integrated chip having an outgas layer and afirst microelectromechanical systems (MEMS) device disposed within afirst cavity, and a getter layer and a second MEMS device disposedwithin a second cavity according to the present disclosure. Although thecross-sectional views 700-2200 shown in FIGS. 7-22 are described withreference to a method, it will be appreciated that the structures shownin FIGS. 7-22 are not limited to the method but rather may stand aloneseparate of the method. Furthermore, although FIGS. 7-22 are describedas a series of acts, it will be appreciated that these acts are notlimiting in that the order of the acts can be altered in otherembodiments, and the methods disclosed are also applicable to otherstructures. In other embodiments, some acts that are illustrated and/ordescribed may be omitted in whole or in part.

As illustrated by the cross-sectional view 700 of FIG. 7, asemiconductor substrate 102 is provided and one or more active elements106 are formed over/within the semiconductor substrate 102. In someembodiments, the one or more active elements 106 may be or comprisetransistors. In such embodiments, source/drain regions 108 of the one ormore active elements 106 may be formed by performing a selective ionimplantation process on the semiconductor substrate 102, therebyimplanting dopants into the semiconductor substrate 102. Further, a gate110 of the one or more active elements 106 may be deposited by chemicalvapor deposition (CVD), physical vapor deposition (PVD), sputtering, oranother suitable growth or deposition process, and subsequentlyperforming a patterning process according to a masking layer (notshown), thereby defining the gate 110.

As illustrated by the cross-sectional view 800 of FIG. 8, aninterconnect structure 104 is formed over the semiconductor substrate102. The interconnect structure 104 includes an interconnect dielectricstructure 115, a plurality of conductive wires 114, and a plurality ofconductive vias 112. In some embodiments, a process for forming theconductive vias and/or wires 112, 114 may, for example, includeperforming a single damascene process and/or a dual damascene processone or more times. In further embodiments, the conductive wires 114include an upper conductive wire layer 114 a. An upper conductive layer116 is formed over the upper conductive wire layer 114 a, and adielectric protection layer 202 is formed over the upper conductivelayer 116. In some embodiments, a process for forming the upperconductive wire layer 114 a, the upper conductive layer 116, and thedielectric protection layer 202 may include: depositing (e.g., CVD, PVD,atomic layer deposition (ALD), sputtering, electroless plating, etc.) astack of layers over an upper surface of the interconnect dielectricstructure 115; forming a masking layer (not shown) over the stack oflayers; exposing unmasked regions of the stack of layers to one or moreetchants, thereby defining the upper conductive wire layer 114 a, theupper conductive layer 116, and the dielectric protection layer 202; andperforming a removal process to remove the masking layer. In someembodiments, the upper conductive wire layer 114 a may, for example, beor comprise copper, aluminum, tungsten, a combination of the foregoing,or the like and/or may be formed to a thickness of about 8,000Angstroms. In some embodiments, the upper conductive layer 116 may, forexample, be or comprise titanium, tantalum, or the like and/or may beformed to a thickness of about 1,800 Angstroms. In some embodiments, thedielectric protection layer 202 may, for example, be or comprise siliconoxy-nitride, silicon nitride, or the like and/or may be formed to athickness of about 320 Angstroms.

As illustrated by the cross-sectional view 900 of FIG. 9, a passivationstructure 118 is formed over the interconnect structure 104. In someembodiments, a process for forming the passivation structure 118 mayinclude forming one or more layers by, for example, CVD, PVD, atomiclayer deposition (ALD), or another suitable deposition process. Infurther embodiments, the passivation structure 118 may include a firstpassivation layer 204, a second passivation layer 206, and a thirdpassivation layer 208. In some embodiments, the first passivation layer204 may, for example, be deposited by plasma-enhanced CVD. In suchembodiments, the first passivation layer 204 may, for example, be orcomprise an oxide, such as silicon dioxide, another suitable oxide, orthe like and/or may be formed to a thickness of about 4,000 Angstroms,12,000 Angstroms, or another suitable thickness. Thus, the firstpassivation layer 204 may be configured as another outgas layercomprising another outgas material with a low outgas depletiontemperature (e.g., about 420 degrees Celsius). In further embodiments,the first passivation layer 204 may, for example, be or comprise silicondioxide and/or may be deposited by high density plasma CVD. In someembodiments, the second passivation layer 206 may, for example, be orcomprise silicon rich oxide, or another suitable dielectric materialand/or may be formed to a thickness of about 1,500 Angstroms. In furtherembodiments, the third passivation layer 208 may, for example, be orcomprise silicon nitride, silicon carbide, or the like and/or may beformed to a thickness of about 4,000 Angstroms.

Also as illustrated in the cross-sectional view 900 of FIG. 9, thepassivation structure 118 is patterned according to a masking layer 904to define an outgas layer opening 902. In some embodiments, thepatterning process may include performing a wet etch and/or a dry etch.An upper surface 204 us of the first passivation layer 204 defines abottom of the outgas layer opening 902. In some embodiments, the uppersurface 204 us of the first passivation layer 204 is separated from anupper surface of the dielectric protection layer 202 by a distance ds.In further embodiments, the distance ds is about 3,400 Angstroms, orwithin a range of about 3,200 to 3,600 Angstroms. In furtherembodiments, after forming the outgas layer opening 902, a removalprocess is performed to remove the masking layer 904 (not shown).

As illustrated by the cross-sectional view 1000 of FIG. 10, an outgasstructure 1002 comprising an outgas material (e.g., amorphous silicon(a-Si)) is formed over the passivation structure 118, thereby fillingthe outgas layer opening 902. In some embodiments, the outgas structure1002 is deposited by a suitable deposition process, such as CVD, PVD,ALD, plasma-enhanced CVD (PECVD), high density plasma (HDP) CVD,sputtering, or another suitable growth or deposition process. In someembodiments, the outgas material is formed by the suitable depositionprocess utilizing a first gas (e.g., SiH_(x), where x is a positivewhole number) as a precursor gas and/or a reacting gas. In someembodiments, the first gas may be or comprise silane (SiH₄). Thus, insome embodiments, the outgas material may, for example, be or compriseamorphous silicon (a-Si), hydrogenated amorphous silicon (e.g., a-Si:H),or the like. For example, the first gas may be silane (SiH₄) and thedeposition process may include reaching a maximum deposition temperature(e.g., less than 500 degrees Celsius). The maximum depositiontemperature and the first gas facilitates the outgas structure 1002comprising amorphous silicon and a high concentration of the outgasspecies (e.g., hydrogen (H)). In some embodiments, the outgas speciesmay fill and/or correct defects (e.g., dangling bonds) present in theoutgas material, thereby reducing the dangling bond density in theoutgas material. In some embodiments, a height h1 between an uppersurface 1002 us of the outgas structure 1002 and the dielectricprotection layer 202 is about 14,000 Angstroms or within a range ofabout 12,000 to 16,000 Angstroms. In further embodiments, a thickness t1of the outgas structure 1002 laterally offset the outgas layer opening902 and overlying an upper surface of the third passivation layer 208 isabout 10,500 Angstroms or within a range of about 8,500 to 12,500Angstroms. In further embodiments, the outgas structure 1002 may bedeposited with a deposition temperature of about 200 degrees Celsius,about 400 degrees Celsius, or another suitable temperature. In someembodiments, depositing the outgas structure 1002 with a depositiontemperature of about 200 degrees Celsius may increase SiH₂ present inthe outgas material after the deposition process. This in turn mayincrease an ability of the outgas material to outgas the outgas species.

As illustrated by the cross-sectional view 1100 of FIG. 11, aplanarization process (e.g., a chemical mechanical planarization (CMP)process) is performed on the outgas structure (1002 of FIG. 10) untilthe upper surface of the passivation structure 118 is reached, therebydefining an outgas layer 130. In some embodiments, due to dishing and/orover-polishing during the planarization process the outgas layer 130 hasa curved or concaved upper surface 130 us, such that the upper surface130 us is disposed below the upper surface of the passivation structure118. In further embodiments, the outgas structure (1002 of FIG. 10) isremoved from the upper surface of the passivation structure 118 inregions laterally offset from the outgas layer opening 902.

In some embodiments, the outgas layer 130 has an outgas depletiontemperature (e.g., about 575 degrees Celsius or greater) greater than amaximum temperature used during subsequent processing steps (e.g., thebonding process of FIG. 20). In some embodiments, due to the depositionprocess of the outgas layer 130 and the amorphous structure of theoutgas material, the outgas material may comprise a-Si, SiH₃, SiH₂,and/or SiH. While the outgas material is exposed to differenttemperatures, it may have different outgas temperature ranges. Forexample, in a first outgas temperature range (e.g., about 350 to 450degrees Celsius) the outgas material may break SiH₃ into SiH₂ and SiHand/or into SiH₂ and H, thereby outgassing the outgas species. Further,in a second outgas temperature range (e.g., about 450 to 575 degreesCelsius), the outgas material may break SiH₂ into Si and SiH and/or intoSiH and H, thereby outgassing the outgas species. Furthermore, in athird outgas temperature range (e.g. about 575 to 725 degrees Celsius),the outgas material may break SiH into Si and H, thereby outgassing theoutgas species. Thus, the outgas layer 130 may outgas the outgas speciesacross a wide range of temperatures and may continue outgassing at highoperating and/or fabrication temperatures.

As illustrated by the cross-sectional view 1200 of FIG. 12, a dielectriccapping layer 210 is formed over the passivation structure 118 and theoutgas layer 130. In some embodiments, the dielectric capping layer 210may, for example, be or comprise silicon nitride, silicon carbide, orthe like and/or may have a thickness of about 3,500 Angstroms or withina range of about 3,000 to 4,000 Angstroms. In some embodiments, thedielectric capping layer 210 may include a capping layer overlying adielectric layer, the capping layer may have a thickness of about 500Angstroms and the dielectric layer may have a thickness of about 3,000Angstroms. In such embodiments, the capping layer and the dielectriclayer comprise a same material (e.g., silicon nitride).

As illustrated by the cross-sectional view 1300 of FIG. 13, a maskinglayer 1302 is formed over the dielectric capping layer 210, where themasking layer 1302 has sidewalls defining one or more openings. In someembodiments, a patterning process is performed on the passivationstructure 118 and the dielectric capping layer 210 according to themasking layer 1302, thereby defining one or more stopper structureopenings 1304. In some embodiments, the patterning process exposes anupper surface of the upper conductive layer 116. In further embodiments,the one or more stopper structure openings 1304 may, for example, eachhave a width w1 of about 2 micrometers or within a range of about 1.9 to2.1 micrometers. In yet further embodiments, if when viewed from abovethe one or more stopper structure openings 1304 are circular then thewidth w1 may correspond to a diameter of the one or more stopperstructure openings 1304. In yet further embodiments, after thepatterning process, a removal process is performed to remove the maskinglayer 1302 (not shown).

As illustrated by the cross-sectional view 1400 of FIG. 14, a firststopper layer 132 a is formed over the dielectric capping layer 210 andthe upper conductive layer 116, further a second stopper layer 132 b isformed over the first stopper layer 132 a. In some embodiments, thefirst and second stopper layers 132 a-b each at least partially fill theone or more stopper structure openings (1304 of FIG. 13). In someembodiments, the first stopper layer 132 a may, for example, be orcomprise titanium, a titanium rich material, tantalum, or the likeand/or may be formed to a thickness of about 130 Angstroms or within arange of about 110 to 150 Angstroms. In some embodiments, the secondstopper layer 132 b may, for example, be or comprise a nitride, such astitanium nitride, tantalum nitride, or the like and/or may be formed toa thickness of about 500 Angstroms or within a range of about 450 to 550Angstroms.

As illustrated by the cross-sectional view 1500 of FIG. 15, a maskinglayer 1502 is formed over the second stopper layer 132 b. The first andsecond stopper layers 132 a, 132 b are patterned according to themasking layer 1502, thereby defining stopper structures 132 overlyingthe upper conductive wire layer 114 a. In some embodiments, after thepatterning process, a removal process is performed to remove the maskinglayer 1502 (not shown).

As illustrated by the cross-sectional view 1600 of FIG. 16, a maskinglayer 1602 is formed over the dielectric capping layer 210 and thestopper structures 132. Further, the passivation structure 118, thedielectric capping layer 210, and the dielectric protection layer 202are patterned according to the masking layer 1602, thereby defining oneor more openings. In some embodiments, the patterning process may exposean upper surface of the upper conductive layer 116 and define a getterlayer 116 a disposed between a stopper structure 132 and the upperconductive wire layer 114 a. In further embodiments, after thepatterning process, a removal process is performed to remove the maskinglayer 1602 (not shown).

As illustrated by the cross-sectional view 1700 of FIG. 17, a maskinglayer 1702 is formed over the dielectric capping layer 210 and thestopper structures 132. Further, the passivation structure 118, thedielectric capping layer 210, the dielectric protection layer 202, andthe upper conductive layer 116 are patterned according to the maskinglayer 1702. In some embodiments, the patterning process may includeperforming a dry etch process, a wet etch process, or another suitableetch process. The masking layer 1702 is configured to protect the getterlayer 116 a during the patterning process of FIG. 17. Further, thepatterning process of FIG. 17 exposes an upper surface and/or sidewallsof the upper conductive wire layer 114 a. In yet further embodiments,after performing the patterning process, a removal process may beperformed to remove the masking layer 1702.

As illustrated by the cross-sectional view 1800 of FIG. 18, an etchprocess is performed on the dielectric capping layer 210, therebyexposing the upper surface 130 us of the outgas layer 130 and exposingan upper surface of the passivation structure 118. In some embodiments,the etch process may be a wet etch, a dry etch, a blanket etch, acombination of the foregoing, or some other suitable etch process.

As illustrated by the cross-sectional view 1900 of FIG. 19, a cappingsubstrate 128 is provided and is subsequently etched to define a firstcavity 136 and a second cavity 140. Further, a capping dielectric layer126 is formed over the upper surface of the capping substrate 128,thereby defining a capping structure 125.

As illustrated by the cross-sectional view 2000 of FIG. 20, a MEMSsubstrate 124 is provided and is subsequently patterned to define one ormore protrusions 124 p. A polysilicon layer 122 is formed over the MEMSsubstrate 124. Conductive bond structures 120 are formed over thepolysilicon layer 122 and continuously extend along the one or moreprotrusions 124 p. Further, an etch process is performed on the MEMSsubstrate 124 to define one or more first moveable elements 134 and oneor more second moveable elements 138.

As illustrated by the cross-sectional view 2100 of FIG. 21, the cappingstructure 125 is flipped, the MEMS substrate 124 is flipped, and thecapping structure 125 is subsequently bonded to the MEMS substrate 124.In some embodiments, bonding the capping structure 125 to the MEMSsubstrate 124 includes performing a fusion bond process. In someembodiments, a maximum temperature of the fusion bond process may bewithin a range of about 150 to 300 degrees Celsius. Thus, the maximumtemperature of the fusion bond process is less than the outgas depletiontemperature of the outgas layer 130, such that the outgas layer 130 mayoutgas the outgas species after bonding the capping structure 125 to theMEMS substrate 124.

As illustrated by the cross-sectional view 2200 of FIG. 22, the MEMSsubstrate 124 is bonded to the interconnect structure 104, therebydefining a device substrate 101, sealing the first and second cavities136, 140, and defining a first MEMS device 135 and a second MEMS device137. In some embodiments, bonding the interconnect structure 104 to theMEMS substrate 124 includes performing a eutectic bond process andreaching a maximum bonding temperature (e.g., about 423 degrees Celsiusor higher) during the eutectic bond process. The maximum bondingtemperature is less than the outgas depletion temperature of the outgaslayer 130, thus the outgas layer 130 may outgas the outgas species afterperforming the eutectic bond process and sealing the first and secondcavities 136, 140. Further, a bonding force may be applied to an uppersurface of the MEMS substrate 124 during the eutectic bond process. Insome embodiments, the bonding force may be within a range of about 30 to40 kilonewtons (kN). In some embodiments, a first bonding pressure(e.g., about 1 atmosphere) surrounds the one or more first and secondmoveable elements 134, 138 during the eutectic bond process.

In some embodiments, the eutectic bond process seals the first cavity136 and the second cavity 140 between the capping structure 125 and thedevice substrate 101, thereby defining the first MEMS device 135 and thesecond MEMS device 137. In some embodiments, the first cavity 136 issealed with a first gas pressure and the second cavity is sealed with asecond gas pressure that is less than the first gas pressure. In furtherembodiments, the maximum temperature of the eutectic bond process isless than the outgas depletion temperature of the outgas layer 130, suchthat the outgas layer 130 may outgas the outgas species after sealingthe first and second cavities 136, 140. In some embodiments, beforeand/or during the eutectic bond process, the first and second cavities136, 140 have an initial gas pressure of about 1 atmosphere. In suchembodiments, after the eutectic bond process, the first gas pressure ofthe first cavity 136 is about 1 atmosphere and the second gas pressureof the second cavity 140 is about 0 atmosphere.

FIG. 23 illustrates a method 2300 of forming an integrated chip havingan outgas layer and a first MEMS device disposed within a first cavity,and a getter layer and a second MEMS device disposed within a secondcavity according to the present disclosure. Although the method 2300 isillustrated and/or described as a series of acts or events, it will beappreciated that the method is not limited to the illustrated orderingor acts. Thus, in some embodiments, the acts may be carried out indifferent orders than illustrated, and/or may be carried outconcurrently. Further, in some embodiments, the illustrated acts orevents may be subdivided into multiple acts or events, which may becarried out at separate times or concurrently with other acts orsub-acts. In some embodiments, some illustrated acts or events may beomitted, and other un-illustrated acts or events may be included.

At act 2302, an interconnect structure is formed over a semiconductorsubstrate. The interconnect structure includes an upper conductive wirelayer. FIG. 8 illustrates a cross-sectional view 800 corresponding tosome embodiments of act 2302.

At act 2304, a passivation structure is formed over the interconnectstructure. FIG. 9 illustrates a cross-sectional view 900 correspondingto some embodiments of act 2304.

At act 2306, the passivation structure is patterned to define an outgaslayer opening overlying the upper conductive wire layer. FIG. 9illustrates a cross-sectional view 900 corresponding to some embodimentsof act 2306.

At act 2308, an outgas structure is formed over the passivationstructure. The passivation structure fills the outgas layer opening andcomprises an outgas material with an outgas depletion temperature. FIG.10 illustrates a cross-sectional view 1000 corresponding to someembodiments of act 2308.

At act 2310, a planarization process is performed on the outgasstructure, thereby defining an outgas layer. FIG. 11 illustrates across-sectional view 1100 corresponding to some embodiments of act 2310.

At act 2312, a capping structure is formed having a first cavity and asecond cavity. FIG. 19 illustrates a cross-sectional view 1900corresponding to some embodiments of act 2312.

At act 2314, a MEMS substrate is provided and subsequently an etchprocess is performed on the MEMS substrate to define one or more firstmoveable elements and one or more second moveable elements. FIG. 20illustrates a cross-sectional view 2000 corresponding to someembodiments of act 2314.

At act 2316, a first bond process is performed to bond the MEMSsubstrate to the capping structure. The first bond process reaches afirst maximum bond temperature less than the outgas depletiontemperature. FIG. 21 illustrates a cross-sectional view 2100corresponding to some embodiments of act 2316.

At act 2318, a second bond process is performed to bond the MEMSsubstrate to the interconnect structure, thereby sealing the first andsecond cavities. The second bond process reaches a second maximum bondtemperature greater than the first maximum bond temperature and lessthan the outgas depletion temperature. FIG. 22 illustrates across-sectional view 2200 corresponding to some embodiments of act 2318.

Accordingly, in some embodiments, the present disclosure relates to anintegrated chip having a first MEMS device disposed within a firstcavity and a second MEMS device disposed within a second cavity. Anoutgas layer abuts the first cavity, such that the first cavity has afirst gas pressure, and a getter layer abuts the second cavity, suchthat the second cavity has a second gas pressure different than thefirst gas pressure.

In some embodiments, the present application provides an integrated chipincluding a device substrate having a first MEMS device and a secondMEMS device laterally offset from the first MEMS device; a cappingstructure overlying the device substrate, wherein the capping structureincludes a first cavity overlying the first MEMS device and a secondcavity overlying the second MEMS device, wherein the first cavity has afirst gas pressure, and wherein the second cavity has a second gaspressure different from the first cavity; and an outgas layer abuttingthe first cavity, wherein the outgas layer includes an outgas materialhaving an outgas species, and wherein the outgas material is amorphous.

In some embodiments, the present application provides an integrated chipincluding a semiconductor substrate including a first material; aninterconnect structure overlying the semiconductor substrate; apassivation structure overlying the interconnect structure; amicroelectromechanical systems (MEMS) substrate overlying theinterconnect structure, wherein the MEMS substrate includes a firstmoveable structure and a second moveable structure laterally offset fromthe first moveable structure; a capping substrate overlying the MEMSsubstrate, wherein the capping substrate includes a first cavityoverlying the first moveable structure and a second cavity overlying thesecond moveable structure, wherein the first cavity has a first gaspressure and the second cavity has a second gas pressure, and whereinthe capping substrate includes the first material; a getter layerdisposed within the second cavity, wherein the getter layer isconfigured to getter an outgas species from the second cavity; and anoutgas layer disposed within the passivation structure and abutting thefirst cavity, wherein the outgas layer is configured to release theoutgas species into the first cavity, such that the first gas pressureis greater than the second gas pressure, wherein the outgas layerincludes a second material, and wherein the second material is anamorphous form of the first material.

In some embodiments, the present application provides a method formanufacturing an integrated chip, the method includes forming aninterconnect structure over a semiconductor substrate; forming apassivation structure over the interconnect structure; forming an outgaslayer in the passivation structure, wherein the outgas layer includes anoutgas material with an outgas depletion temperature; forming a cappingstructure comprising a first cavity and a second cavity; forming amicroelectromechanical systems (MEMS) substrate including a firstmoveable structure and a second moveable structure; performing a firstbonding process to bond the MEMS substrate to the capping structure,wherein the first bonding process reaches a first maximum bondingtemperature less than the outgas depletion temperature; and performing asecond bonding process to bond the MEMS substrate to the interconnectstructure, wherein the first cavity overlies the first moveablestructure and the second cavity overlies the second moveable structure,wherein the second bonding process reaches a second maximum bondingtemperature less than the outgas depletion temperature, and wherein thesecond bonding process seals the first cavity with a first gas pressureand seals the second cavity with a second gas pressure.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated chip, comprising: a devicesubstrate comprising a first microelectromechanical systems (MEMS)device and a second MEMS device laterally offset from the first MEMSdevice; a capping structure overlying the device substrate, wherein thecapping structure comprises a first cavity overlying the first MEMSdevice and a second cavity overlying the second MEMS device, wherein thefirst cavity has a first gas pressure, and wherein the second cavity hasa second gas pressure different from the first cavity; and an outgaslayer abutting the first cavity, wherein the outgas layer comprises anoutgas material having an outgas species, and wherein the outgasmaterial is amorphous.
 2. The integrated chip of claim 1, wherein theoutgas material comprises hydrogenated amorphous silicon and the outgasspecies comprises hydrogen.
 3. The integrated chip of claim 1, whereinthe device substrate comprises: a semiconductor substrate, aninterconnect structure overlying the semiconductor substrate, whereinthe interconnect structure comprises an interconnect dielectricstructure and a top conductive wire layer disposed along an uppersurface of the interconnect dielectric structure; a passivationstructure overlying the interconnect dielectric structure; a MEMSsubstrate disposed between the interconnect structure and the cappingstructure, wherein the MEMS substrate comprises a first moveablestructure of the first MEMS device and a second moveable structure ofthe second MEMS device; and wherein the outgas layer is disposed withinthe passivation structure vertically above the top conductive wirelayer.
 4. The integrated chip of claim 3, further comprising: a getterlayer abutting the second cavity, wherein the getter layer is configuredto getter the outgas species from the second cavity; and wherein theoutgas layer is configured to outgas the outgas species into the firstcavity such that the first gas pressure is greater than the second gaspressure.
 5. The integrated chip of claim 4, wherein the first gaspressure is approximately 1 atmosphere and the second gas pressure isapproximately 0 atmosphere.
 6. The integrated chip of claim 3, whereinthe semiconductor substrate comprises a crystalline form of the outgasmaterial.
 7. The integrated chip of claim 3, further comprising: a firststopper structure disposed within the first cavity and underlying thefirst moveable structure; and a second stopper structure disposed withthe second cavity and underlying the second moveable structure.
 8. Theintegrated chip of claim 1, wherein the first MEMS device is anaccelerometer and the second MEMS device is a gyroscope.
 9. Theintegrated chip of claim 1, further comprising: a polysilicon layerdisposed between the capping structure and the outgas layer, wherein thepolysilicon layer comprises a crystalline form of the outgas material.10. An integrated chip, comprising: a device substrate comprising afirst microelectromechanical systems (MEMS) device and a second MEMSdevice laterally offset from the first MEMS device; a capping structureoverlying the device substrate, wherein the capping structure comprisesa first cavity overlying the first MEMS device and a second cavityoverlying the second MEMS device, wherein the first cavity has a firstgas pressure, and wherein the second cavity has a second gas pressuredifferent from the first cavity; and an outgas layer abutting the firstcavity, wherein the outgas layer comprises an outgas material having anoutgas species, and wherein the outgas material is amorphous, whereinthe outgas material comprises amorphous silicon.
 11. The integrated chipof claim 10, wherein the device substrate comprises: a semiconductorsubstrate, an interconnect structure overlying the semiconductorsubstrate, wherein the interconnect structure comprises an interconnectdielectric structure and a top conductive wire layer disposed along anupper surface of the interconnect dielectric structure; a passivationstructure overlying the interconnect dielectric structure; a MEMSsubstrate disposed between the interconnect structure and the cappingstructure, wherein the MEMS substrate comprises a first moveablestructure of the first MEMS device and a second moveable structure ofthe second MEMS device; and wherein the outgas layer is disposed withinthe passivation structure vertically above the top conductive wirelayer.
 12. The integrated chip of claim 11, further comprising: a getterlayer abutting the second cavity, wherein the getter layer is configuredto getter the outgas species from the second cavity; and wherein theoutgas layer is configured to outgas the outgas species into the firstcavity such that the first gas pressure is greater than the second gaspressure.
 13. The integrated chip of claim 12, wherein the first gaspressure is approximately 1 atmosphere and the second gas pressure isapproximately 0 atmosphere.
 14. The integrated chip of claim 11, whereinthe semiconductor substrate comprises a crystalline form of the outgasmaterial.
 15. An integrated chip, comprising: a semiconductor substratecomprising a first material; an interconnect structure overlying thesemiconductor substrate; a passivation structure overlying theinterconnect structure; a microelectromechanical systems (MEMS)substrate overlying the interconnect structure, wherein the MEMSsubstrate comprises a first moveable structure and a second moveablestructure laterally offset from the first moveable structure; a cappingsubstrate overlying the MEMS substrate, wherein the capping substratecomprises a first cavity overlying the first moveable structure and asecond cavity overlying the second moveable structure, wherein the firstcavity has a first gas pressure and the second cavity has a second gaspressure, and wherein the capping substrate comprises the firstmaterial; a getter layer disposed within the second cavity, wherein thegetter layer is configured to getter an outgas species from the secondcavity; and an outgas layer disposed within the passivation structureand abutting the first cavity, wherein the outgas layer is configured torelease the outgas species into the first cavity, such that the firstgas pressure is greater than the second gas pressure, wherein the outgaslayer comprises a second material, and wherein the second material is anamorphous form of the first material.
 16. The integrated chip of claim15, wherein the first material comprises crystalline silicon and thesecond material comprises hydrogenated amorphous silicon.
 17. Theintegrated chip of claim 15, wherein an upper surface of the getterlayer is substantially flat and an upper surface of the outgas layer iscurved.
 18. The integrated chip of claim 15, further comprising: a firststopper structure underlying the first moveable structure and abuttingthe first cavity; a bonding structure laterally offset from the firstmoveable structure; and wherein the outgas layer is spaced laterallybetween the bonding structure and the first stopper structure.
 19. Theintegrated chip of claim 18, further comprising: a second stopperstructure underlying the second moveable structure and abutting thesecond cavity; and wherein the getter layer is disposed between thesecond stopper structure and the interconnect structure.
 20. Theintegrated chip of claim 18, wherein a bottom surface of the bondingstructure is vertically below a bottom surface of the outgas layer and atop surface of the bonding structure is vertically above a top surfaceof the outgas layer.